Difference between revisions of "Surficial geochemical interpretation guidelines"
Jump to navigation
Jump to search
FWhitehurst (talk | contribs) |
Cwhitehurst (talk | contribs) |
||
| (9 intermediate revisions by 3 users not shown) | |||
| Line 6: | Line 6: | ||
| part = Predicting the occurrence of oil and gas traps | | part = Predicting the occurrence of oil and gas traps | ||
| chapter = Surface geochemical exploration for petroleum | | chapter = Surface geochemical exploration for petroleum | ||
| − | | frompg = 18- | + | | frompg = 18-19 |
| − | | topg = 18- | + | | topg = 18-19 |
| author = Dietmar Schumacher | | author = Dietmar Schumacher | ||
| link = http://archives.datapages.com/data/specpubs/beaumont/ch18/ch18.htm | | link = http://archives.datapages.com/data/specpubs/beaumont/ch18/ch18.htm | ||
| Line 14: | Line 14: | ||
| isbn = 0-89181-602-X | | isbn = 0-89181-602-X | ||
}} | }} | ||
| − | The presence of hydrocarbon macroseeps or microseeps in the area of a geochemical survey is direct evidence that petroleum has been generated. Hydrocarbon seepage at the surface represents the end of a petroleum migration pathway. These hydrocarbons may represent hydrocarbon leakage from an [[accumulation]] or leakage along a carrier bed or other migration pathway. Anomalies defined by multiple samples from one or more survey lines may indicate the location of discrete structural or stratigraphic targets within the survey area. | + | The presence of hydrocarbon macroseeps or microseeps in the area of a geochemical survey is direct evidence that petroleum has been generated. Hydrocarbon seepage at the surface represents the end of a petroleum [[migration pathway]]. These hydrocarbons may represent hydrocarbon leakage from an [[accumulation]] or leakage along a carrier bed or other migration pathway. Anomalies defined by multiple samples from one or more survey lines may indicate the location of discrete structural or stratigraphic targets within the survey area. |
==Anomalies and vertical migration== | ==Anomalies and vertical migration== | ||
| Line 20: | Line 20: | ||
==Anomalies and lateral migration== | ==Anomalies and lateral migration== | ||
| − | If the structural or geologic setting of the area suggests that microseepage may be predominantly lateral or pathway selective, such as along dipping stratigraphic surfaces and [[Unconformity|unconformities]], the interpretation will be more difficult since geochemical anomalies may then not be located vertically above a trap. Which of these migration scenarios is more likely in your area of investigation? What is the relationship of the anomalies to outcrop geology, mapped structural closures, stratigraphic pinch-outs, faults, or basement highs? Because relationships between surface geochemical anomalies and subsurface [[accumulation]]s can be complex, proper interpretation requires integration of surface geochemical data with geologic, geophysical, and hydrologic data. The importance of such integration cannot be overstated.<ref name=ch18r46>Thrasher, J., A., Fleet, A., J., Hay, S., J., Hovland, M., Duppenbecker, S., 1996, [http://archives.datapages.com/data/specpubs/memoir66/17/0223.htm Understanding geology as the key to using seepage in exploration: the spectrum of seepage styles], in | + | If the structural or geologic setting of the area suggests that microseepage may be predominantly [[lateral]] or pathway selective, such as along dipping stratigraphic surfaces and [[Unconformity|unconformities]], the interpretation will be more difficult since geochemical anomalies may then not be located vertically above a trap. Which of these migration scenarios is more likely in your area of investigation? What is the relationship of the anomalies to [http://www.merriam-webster.com/dictionary/outcrop outcrop] geology, mapped structural closures, stratigraphic pinch-outs, faults, or [[basement]] highs? Because relationships between surface geochemical anomalies and subsurface [[accumulation]]s can be complex, proper interpretation requires integration of surface geochemical data with geologic, geophysical, and hydrologic data. The importance of such integration cannot be overstated.<ref name=ch18r46>Thrasher, J., A., Fleet, A., J., Hay, S., J., Hovland, M., Duppenbecker, S., 1996, [http://archives.datapages.com/data/specpubs/memoir66/17/0223.htm Understanding geology as the key to using seepage in exploration: the spectrum of seepage styles], in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 223–241</ref> |
==Hydrocarbon composition from macroseeps== | ==Hydrocarbon composition from macroseeps== | ||
| − | Hydrocarbon seep composition can play an important role in evaluating the exploration potential of a basin, play, or prospect. Petroleum in most visible oil and gas seeps (i.e., macroseeps) generally has been altered by processes such as biodegradation, water washing, and evaporative loss of volatile components. Despite these changes, chemical and iso-topic analysis of such seeps can enable inferences about the nature of the source rock facies and maturity as well as permit correlation with known source rocks and reservoired petroleum. | + | Hydrocarbon seep composition can play an important role in evaluating the exploration potential of a basin, play, or prospect. Petroleum in most visible oil and gas seeps (i.e., macroseeps) generally has been altered by processes such as [[biodegradation]], water washing, and evaporative loss of volatile components. Despite these changes, chemical and iso-topic analysis of such seeps can enable inferences about the nature of the source rock facies and maturity as well as permit correlation with known source rocks and reservoired petroleum. |
==Hydrocarbon composition from microseeps== | ==Hydrocarbon composition from microseeps== | ||
| − | Obtaining compositional information from the analysis of hydrocarbon microseeps is more difficult because microseeps generally consist of only light hydrocarbons (methane through pentane). Sometimes, however, the heavier gasoline-range and aromatic hydrocarbons are also present. One can infer the composition of the migrating petroleum from these light hydrocarbons from soil gas/hydrocarbon ratios, carbon isotopic composition of soil gases, fluorescence characteristics of soil or sediment extracts, and chromatographic analysis of such extracts. A detailed discussion of these methodologies is beyond the scope of this article, but published examples of such analyses and their interpretations include Abrams<ref name=ch18r3>Abrams, M., A., 1996, [http://archives.datapages.com/data/specpubs/memoir66/22/0309.htm Interpretation of methane carbon isotopes extracted from surficial marine sediments for detection of subsurface hydrocarbons], in | + | Obtaining compositional information from the analysis of hydrocarbon microseeps is more difficult because microseeps generally consist of only light hydrocarbons (methane through pentane). Sometimes, however, the heavier gasoline-range and aromatic hydrocarbons are also present. One can infer the composition of the migrating petroleum from these light hydrocarbons from soil gas/hydrocarbon ratios, carbon isotopic composition of soil gases, fluorescence characteristics of soil or sediment extracts, and chromatographic analysis of such extracts. A detailed discussion of these methodologies is beyond the scope of this article, but published examples of such analyses and their interpretations include Abrams<ref name=ch18r3>Abrams, M., A., 1996, [http://archives.datapages.com/data/specpubs/memoir66/22/0309.htm Interpretation of methane carbon isotopes extracted from surficial marine sediments for detection of subsurface hydrocarbons], in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 309–318.</ref> Barwise and Hay<ref name=ch18r6>Barwise, T., Hay, S., 1996, [http://archives.datapages.com/data/specpubs/memoir66/28/0363.htm Predicting oil properties from core fluorescence], in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 363–371.</ref> Belt and Rice<ref name=ch18r8>Belt, J., Q., Rice, G., K., 1996, Offshore 3D seismic, geochemical data integration, Main Pass project, Gulf of Mexico: Oil & Gas Journal, vol. 94, no. 14, p. 76–81, and vol. 94, no. 15, p. 100–102.</ref> Brooks et al.<ref name=ch18r9>Brooks, J., M., Kennicutt, M., C., Carey, B., D., 1986, Offshore surface geochemical exploration: Oil & Gas Journal, October 20, p. 66–72.</ref> Horvitz<ref name=ch18r16>Horvitz, L., 1985, Geochemical exploration for petroleum: Science, vol. 229, p. 821–827.</ref> Jones and Drozd<ref name=ch18r17>Jones, V., T., and R. J. Drozd, 1983, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0067/0006/0900/0932.htm Predictions of oil or gas potential by near-surface geochemistry]: AAPG Bulletin, vol. 67, p. 932–952.</ref> Kornacki<ref name=ch18r20>Kornacki, A., S., 1996, [http://archives.datapages.com/data/specpubs/memoir66/32/0413.htm Petroleum geology and geochemistry of Miocene source rocks and heavy petroleum samples from Huasna Basin, California], in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 413–430.</ref> Piggot and Abrams<ref name=ch18r28>Piggott, N., Abrams, M., A., 1996, [http://archives.datapages.com/data/specpubs/memoir66/30/0385.htm Near-surface coring in the Beaufort and Chukchi Seas, northern Alaska], in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 385–399.</ref> Schiemer et al.<ref name=ch18r38>Schiemer, E., J., Stober, G., Faber, E., 1985, Surface geochemical exploration for hydrocarbons in offshore areas—principles, methods and results, in Petroleum Geochemistry in Exploration of the Norwegian Shelf: London, Graham and Trotman, p. 223–238.</ref> Stahl et al.<ref name=ch18r42>Stahl, W., Faber, E., Carey, B., D., Kirksey, D., L., 1981, [http://archives.datapages.com/data/bulletns/1980-81/data/pg/0065/0009/1500/1543.htm Near-surface evidence of migration of natural gas from deep reservoirs and source rocks]: AAPG Bulletin, vol. 65, p. 1543–1550.</ref> and Thrasher et al.<ref name=ch18r45>Thrasher, J., A., Strait, D., Lugo, R., A., 1996a, [http://archives.datapages.com/data/specpubs/memoir66/29/0373.htm Surface geochemistry as an exploration tool in the South Caribbean], in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 373–384.</ref> |
==See also== | ==See also== | ||
| Line 44: | Line 44: | ||
[[Category:Predicting the occurrence of oil and gas traps]] | [[Category:Predicting the occurrence of oil and gas traps]] | ||
[[Category:Surface geochemical exploration for petroleum]] | [[Category:Surface geochemical exploration for petroleum]] | ||
| + | [[Category:Treatise Handbook 3]] | ||
Latest revision as of 22:24, 31 January 2022
| Exploring for Oil and Gas Traps | |
| |
| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Predicting the occurrence of oil and gas traps |
| Chapter | Surface geochemical exploration for petroleum |
| Author | Dietmar Schumacher |
| Link | Web page |
| Store | AAPG Store |
The presence of hydrocarbon macroseeps or microseeps in the area of a geochemical survey is direct evidence that petroleum has been generated. Hydrocarbon seepage at the surface represents the end of a petroleum migration pathway. These hydrocarbons may represent hydrocarbon leakage from an accumulation or leakage along a carrier bed or other migration pathway. Anomalies defined by multiple samples from one or more survey lines may indicate the location of discrete structural or stratigraphic targets within the survey area.
Anomalies and vertical migration
If the basin or play is characterized by predominantly vertical migration, then the correlation of a strong geochemical anomaly at the surface with a possible trap at depth suggests that the trap is charged with hydrocarbons. Conversely, if the trap is not associated with a positive geochemical anomaly, we assume the trap is not charged with hydrocarbons.
Anomalies and lateral migration
If the structural or geologic setting of the area suggests that microseepage may be predominantly lateral or pathway selective, such as along dipping stratigraphic surfaces and unconformities, the interpretation will be more difficult since geochemical anomalies may then not be located vertically above a trap. Which of these migration scenarios is more likely in your area of investigation? What is the relationship of the anomalies to outcrop geology, mapped structural closures, stratigraphic pinch-outs, faults, or basement highs? Because relationships between surface geochemical anomalies and subsurface accumulations can be complex, proper interpretation requires integration of surface geochemical data with geologic, geophysical, and hydrologic data. The importance of such integration cannot be overstated.[1]
Hydrocarbon composition from macroseeps
Hydrocarbon seep composition can play an important role in evaluating the exploration potential of a basin, play, or prospect. Petroleum in most visible oil and gas seeps (i.e., macroseeps) generally has been altered by processes such as biodegradation, water washing, and evaporative loss of volatile components. Despite these changes, chemical and iso-topic analysis of such seeps can enable inferences about the nature of the source rock facies and maturity as well as permit correlation with known source rocks and reservoired petroleum.
Hydrocarbon composition from microseeps
Obtaining compositional information from the analysis of hydrocarbon microseeps is more difficult because microseeps generally consist of only light hydrocarbons (methane through pentane). Sometimes, however, the heavier gasoline-range and aromatic hydrocarbons are also present. One can infer the composition of the migrating petroleum from these light hydrocarbons from soil gas/hydrocarbon ratios, carbon isotopic composition of soil gases, fluorescence characteristics of soil or sediment extracts, and chromatographic analysis of such extracts. A detailed discussion of these methodologies is beyond the scope of this article, but published examples of such analyses and their interpretations include Abrams[2] Barwise and Hay[3] Belt and Rice[4] Brooks et al.[5] Horvitz[6] Jones and Drozd[7] Kornacki[8] Piggot and Abrams[9] Schiemer et al.[10] Stahl et al.[11] and Thrasher et al.[12]
See also
- Surficial geochemistry and hydrocarbon detection methods
- Surficial geochemical survey objectives
- Selecting a surficial geochemistry survey method
- Designing a surficial geochemical survey
References
- ↑ Thrasher, J., A., Fleet, A., J., Hay, S., J., Hovland, M., Duppenbecker, S., 1996, Understanding geology as the key to using seepage in exploration: the spectrum of seepage styles, in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: AAPG Memoir 66, p. 223–241
- ↑ Abrams, M., A., 1996, Interpretation of methane carbon isotopes extracted from surficial marine sediments for detection of subsurface hydrocarbons, in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: AAPG Memoir 66, p. 309–318.
- ↑ Barwise, T., Hay, S., 1996, Predicting oil properties from core fluorescence, in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: AAPG Memoir 66, p. 363–371.
- ↑ Belt, J., Q., Rice, G., K., 1996, Offshore 3D seismic, geochemical data integration, Main Pass project, Gulf of Mexico: Oil & Gas Journal, vol. 94, no. 14, p. 76–81, and vol. 94, no. 15, p. 100–102.
- ↑ Brooks, J., M., Kennicutt, M., C., Carey, B., D., 1986, Offshore surface geochemical exploration: Oil & Gas Journal, October 20, p. 66–72.
- ↑ Horvitz, L., 1985, Geochemical exploration for petroleum: Science, vol. 229, p. 821–827.
- ↑ Jones, V., T., and R. J. Drozd, 1983, Predictions of oil or gas potential by near-surface geochemistry: AAPG Bulletin, vol. 67, p. 932–952.
- ↑ Kornacki, A., S., 1996, Petroleum geology and geochemistry of Miocene source rocks and heavy petroleum samples from Huasna Basin, California, in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: AAPG Memoir 66, p. 413–430.
- ↑ Piggott, N., Abrams, M., A., 1996, Near-surface coring in the Beaufort and Chukchi Seas, northern Alaska, in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: AAPG Memoir 66, p. 385–399.
- ↑ Schiemer, E., J., Stober, G., Faber, E., 1985, Surface geochemical exploration for hydrocarbons in offshore areas—principles, methods and results, in Petroleum Geochemistry in Exploration of the Norwegian Shelf: London, Graham and Trotman, p. 223–238.
- ↑ Stahl, W., Faber, E., Carey, B., D., Kirksey, D., L., 1981, Near-surface evidence of migration of natural gas from deep reservoirs and source rocks: AAPG Bulletin, vol. 65, p. 1543–1550.
- ↑ Thrasher, J., A., Strait, D., Lugo, R., A., 1996a, Surface geochemistry as an exploration tool in the South Caribbean, in D. Schumacher, and M. A. Abrams, eds., Hydrocarbon Migration and Its Near-Surface Expression: AAPG Memoir 66, p. 373–384.
External links
| find literature about Surficial geochemical interpretation guidelines |
|
|
|
|